Which constitutional Amendment Act of India reduced voting age Act of India reduced voting age from 21 years to 18 years?

Which constitutional Amendment Act of India reduced voting age Act of India reduced voting age from 21 years to 18 years? [SSC CAPF’s ASI & Delhi Police SI Exam 01/07/2017, Shift I], [SSC CHSL (10 + 2) DEO & LDC Exam 28/10/2012], [SSC CHSL (10 + 2) DEO & LDC, PA/SA Exam 15/11/2015]

          a) 42^nd Amendments Act

          b) 61^st Amendment Act

          c) 74^th Amendment Act

          d) 83^rd Amendment Act